Safety pilot



Aug. 25, 1 6 R. s. LOVELAND SAFETY PILOT Filed May 15, 1961 INVENTOR.

ROGER S. LOVEEAND zzfid ATTORNEY United States Patent 3,145,763 SAFETY PILOT Roger S. Loveland, Torrance, Califi, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Filed May 15, 1961, Ser. No. 109,979 Claims. (Cl. 158123) This invention relates to safety pilots and, more particularly, to a pilot burner and thermocouple combination which is used to ignite a main burner and to control a safety valve which, in turn, controls the flow of gas to the main burner. Safety pilots of this general kind are well known in the art and this particular invention is an improvement over, or a smaller version of, a somewhat similar safety pilot illustrated and described in a copending application of Roger S. Loveland and Nicholas J. Sidaris, Serial No. 790,438, filed February 2, 1959, now Patent No. 3,056,450.

As gas burner appliances are becoming smaller and smaller in size, there is a constant demand for the controls for such burners to be reduced in size, consume less gas, and yet be as reliable in operation as controls much larger in size. This is quite a problem but it is deemed to be accomplished by this invention, the burner diameter and length of which is approximately one-half of that of the above mentioned invention of Loveland et al.

One of the objects of this invention is to produce a very small and non-aerated safety pilot which uses less gas than comparable prior art devices.

Another object of the invention is to produce a very small safety pilot of low B.t.u. output which has excellent flame retention characteristics and is of inexpensive construction.

Still another object of the invention is to produce an inexpensive safety pilot which, due to its construction, requires no gas divider or spreader to provide a proper flame for heating a flame sensor and for igniting a main burner.

A still further object of the invention is to provide a safety pilot of small size wherein the conduit for supplying gas to the pilot burner head is attached to the side thereof and serves as the support means therefor.

Other objects of the invention will become apparent upon reading the following detailed description of the invention in conjunction with the accompanying drawing wherein:

FIGURE 1 is a side elevational View of the invention;

FIGURE 2 is an enlarged vertical sectional View of the invention with portions thereof broken away; and

FIGURE 3 is a cross sectional view taken along line 3-3 of FIGURE 2.

The invention is shown as twice its actual size in FIG- URE 1 of the drawing. It comprises a bracket 11 having a downwardly extending skirt portion 11a and an upwardly and outwardly inclined extension 11b. The skirt portion 11a has an aperture 12 therein which is adapted to receive a bolt (not shown) for securing the bracket to a main burner assembly (not shown). The extension 1112 has an aperture therein through which a conduit 13 extends. The conduit is secured in the extension 1112 by means of welding or brazing at points 14 and 15. The upper end of the conduit 13 is closed at 13a and has an opening 13b therein near the closed end to receive the inlet sleeve 16a of a burner head generally designated by the reference numeral 17. The head is secured to the conduit by welding the sleeve 16a thereto at 18.

The sleeve 16a is an extruded portion from an outer tube 16 of the burner head and is located near the bottom thereof and slightly above an inwardly extending annular flange 16b at the bottom of the tube. The inner edge of the flange 16b terminates in an upwardly extending lip 3,145,763 Patented Aug. 25, 1964 portion 16c for a purpose to be presently described. The upper end of the tube 16 has an outwardly extending and upwardly bowed annular flange 16d which serves as a draft shield and a flame spreader or divider. A short distance below the flange 16d are three arcuate slots 18 of substantially equal length and approximately ninety-eight degrees between their centers in a plane substantially perpendicular to the axis of tube 16. The center slot has its center substantially diametrically opposite the center of the sleeve 16a. The land portions of the tube 16 between the slots 13 and 19 and between the slots 19 and 20 are relatively narrow while the land portion between the slots 18 and 20 is considerably larger than the other land portions.

Positioned co-axially within the tube 16 is a smaller diameter tube 21 having an inner diameter the same as the larger diameter of the lip portion of the tube 16 and an outer diameter substantially less than the inner diameter of the tube 16 to provide an annular chamber between the tubes 21 and 16. The lower end of the tube 21 rests in sealing engagement on the upper surface of the flange portion 16b and at the base of the lip portion 160. The upper end of the tube 21 has an outwardly extending annular flange 21a that has an outer diameter very slightly larger than the inner diameter of the tube 16 so that the flange 21a fits within the tube 16 with an interference and sealing fit so as to hold it in its assembled relationship within the tube 16. The length of the tube 21 is such that the upper surface of the flange 21a is substantially in alignment with the lower edge of the flange 16b. There are three arcuate slots 22, 23, and 24 of substantially equal length that are disposed with the same angular relationship as the slots 18, 19, and 20 but which are of shorter length than the outer slots and have less long land portions therebetween than the outer slots. The longitudinal axes also lie in a plane which is substantially in alignment with the lower edge of the slots 18, 19, and 20. This positions the axes of the inner slots slightly below the axes of the outer slots.

Secured within an opening 11c in the bracket 11 is a supporting tube 25 for a flame sensing unit 26. The tube 25 is secured to the bracket by a weld joint 27 so that the axis of the tube 25 is coaxial with the axis of the tubes 16 and 21. The flame sensing unit 26 is illustrated in the drawing as being a thermocouple having an outer concentric lead 26a. The lead is surrounded by a ring nut 28 that is screw threaded into the bottom of the tube 25 to hold the thermocouple in assembled relationship with respect to the burner. As the flame sensing unit per se is of conventional construction, it will suflice to state that it projects through the burner head 17 a short distance above the top thereof and is of an outside diameter, where it passes through the burner head, slightly less than the diameter of the inner edge of the lip portion 160.

Gas is supplied to the burner tube 13 through a coupling 29 having an external thread 29a thereon and an internally threaded coupling 30 surrounding a gas supply conduit 31. An orifice member (not shown) is positioned within the couplings 29 and 30 for regulating the gas flow to the burner head 17 With the safety pilot installed in a heating system so that the burner head 17 is close to a main burner, the thermocouple lead 26a connected to a safety valve in a gas line and the conduit 31 connected to the gas line, gas will flow into the chamber between the tube 16 and 21 and out through all of the arcuate slots to provide a plurality of inwardly directed flames and outwardly directed flames which rise above the burner head and rejoin at or near the upper end of the flame sensing unit to form a substantially annular flame. The flames from the slots 23 and 19 will be only slightly less high than those from the slots 18 and 22 and 24 and 20 but due to the fact that the last mentioned slots are required to heat a greater area of the flame sensing unit, including that above the land between the slots 22 and 24, the flame sensing unit will be heated substantially uniformly completely around the upper end thereof. As this is a so-called atmospheric type of burner, wherein the drop in pressure between the annular chamber and the exterior of the burner head is very slight, it is believed that the distribution of gas around the burner head is due to the combined structural features of the inner and outer slots being slightly mis-aligned as well as there being a much longer land portion between the slots 20 and 18 and slots 22 and 24 in the outer and inner burner tubes, respectively. It is to be noted that there is no gas dividing or spreading means between the inlet 16a of the burner head and the arcuate slot outlets of the burner head, as have been required in prior art atmospheric burners having long or widely spaced burner ports. Regardless of the theory of operation of the burner head, it has been found that this particular burner head construction does provide very satisfactory heating of a flame responsive device, such as the preferred embodiment, a thermocouple sensing unit, to provide reliable safe control of the main burner gas. The flange 16d, on the burner head, serves the dual function of protecting the outer arcuate slots from downdrafts, that would tend to extinguish them, as well as causing the flame to come closer to the main burner orifices to ignite the gas issuing from the main burner.

While the preferred embodiment of the invention has been described above, it is deemed to be apparent that some modification could be made therein without departing from the spirit of the invention. Therefore, the scope of the invention should be determined from the appended claims.

I claim as my invention:

1. A safety pilot comprising a mounting bracket, means on said bracket for supporting a flame sensing unit thereon, a flame sensing unit on said means, a pilot burner surrounding said unit intermediate its ends and radially spaced therefrom, and conduit means mounted on said bracket and connected to said pilot burner for conducting gas thereto, said pilot burner having inner and outer annular walls providing an annular chamber therebetween, means providing a gas flow connection between said annular chamber and said conduit means, said outer wall having an outwardly extending annular flange at its upper end, means closing the spaces between the upper and lower ends of said walls, a plurality of arcuate slots near the upper end of said inner wall and positioned to direct flames onto said flame sensing unit, and a plurality of arcuate slots in said outer wall near said outwardly extending annular flange with their longitudinal axes axially oflset slightly with respect to the longitudinal axes of the arcuate slots in said inner wall.

2. A safety pilot as defined in claim 1 wherein said flame sensing unit is elongated and extends through and slightly above said pilot burner.

3. A safety pilot comprising a mounting bracket, a flame sensing unit, means on said bracket for supporting said flame sensing unit thereon, a pilot burner surrounding said unit intermediate its ends and spaced radially therefrom to provide a space therebetween, and conduit means mounted on said bracket and connected to said pilot burner for conducting gas thereto, said pilot burner comprising an inner tube having an outwardly extending annular flange at its upper end, an outwardly spaced outer tube with an outwardly extending annular flange at its upper end and an inwardly extending annular flange at its lower end, a plurality of arcuate slots near the upper end of said inner tube and a plurality of arcuate slots in said outer tube circumferentially aligned and axially offset with respect to the arcuate slots in said inner tube, and a gas flow connection between said conduit means and the space between said inner and outer tubes.

4. The combination comprising a bracket, an elongated flame sensing unit mounted on said bracket, a pilot burner surrounding said unit intermediate its ends and spaced radially therefrom to provide a space therebetween, and conduit means mounted on said bracket and connected to said pilot burner for conducting gas thereto, said pilot burner comprising an inner tube having an outwardly extending annular flange at its upper end, an outwardly spaced outer tube engaging said outwardly extending annular flange and having an outwardly extending annular flange at its upper end and an inwardly extending annular flange at its lower end which engages the lower end of said inner tube, a gas flow connection between said conduit means and the space between said inner and outer tubes, a plurality of arcuate slots near the upper end of said inner tube and a plurality of arcuate slots in said outer tube circumferentially aligned and axially offset with respect to the arcuate slots in said inner tube.

5. The combination defined in claim 4 wherein the centers of said arcuate slots are approximately equidistant apart in each tube, leaving a wide land portion between the slots nearest the conduit means and narrow land portions between the other slots.

References Cited in the file of this patent UNITED STATES PATENTS 2,267,742 Mantz Dec. 30, 1941 2,311,778 Reinhart Feb. 23, 1943 2,335,471 Ashcraft Nov. 30, 1943 2,474,547 Patch June 28, 1949 12,627,308 Clark Feb. 3, 1953 2,649,490 Greenamyer Aug. 18, 1953 2,710,055 Betz June 7, 1955 

1. A SAFETY PILOT COMPRISING A MOUNTING BRACKET, MEANS ON SAID BRACKET FOR SUPPORTING A FLAME SENSING UNIT THEREON, A FLAME SENSING UNIT ON SAID MEANS, A PILOT BURNER SURROUNDING SAID UNIT INTERMEDIATE ITS ENDS AND RADIALLY SPACED THEREFROM, AND CONDUIT MEANS MOUNTED ON SAID BRACKET AND CONNECTED TO SAID PILOT BURNER FOR CONDUCTING GAS THERETO, SAID PILOT BURNER HAVING INNER AND OUTER ANNULAR WALLS PROVIDING AN ANNULAR CHAMBER THEREBETWEEN, MEANS PROVIDING A GAS FLOW CONNECTION BETWEEN SAID ANNULAR CHAMBER AND SAID CONDUIT MEANS, SAID OUTER WALL HAVING AN OUTWARDLY EXTENDING ANNULAR FLANGE AT ITS UPPER END, MEANS CLOSING THE SPACES BETWEEN THE UPPER AND LOWER ENDS OF SAID WALLS, A PLURALITY OF ARCUATE SLOTS NEAR THE UPPER END OF SAID INNER WALL AND POSITIONED TO DIRECT FLAMES ONTO SAID FLAME SENSING UNIT, AND A PLURALITY OF ARCUATE SLOTS IN SAID OUTER WALL NEAR SAID OUTWARDLY EXTENDING ANNULAR FLANGE WITH THEIR LONGITUDINAL AXES AXIALLY OFFSET SLIGHTLY WITH RESPECT TO THE LONGITUDINAL AXES OF THE ARCUATE SLOTS IN SAID INNER WALL. 